Generated by AskSia.ai — graphs, formulas, traps
| Feature | Prokaryote | Eukaryote |
|---|---|---|
| Nucleus | none (nucleoid) | membrane-bound |
| Organelles | none | many |
| Size | 1-10 µm | 10-100 µm |
| DNA | circular | linear, multiple chromosomes |
| Ribosome | 70S | 80S |
| Organelle | Function |
|---|---|
| Nucleus | DNA storage, transcription |
| Mitochondrion | ATP via oxidative phos (own DNA) |
| Chloroplast | photosynthesis (plants, own DNA) |
| Ribosome | protein synthesis |
| Rough ER | protein synthesis + folding |
| Smooth ER | lipid synth, detox |
| Golgi | modify + ship proteins |
| Lysosome | digestion (animals) |
Transport: passive (no ATP) = simple diffusion, facilitated diffusion, osmosis. Active (ATP) = pumps (Na⁺/K⁺), endocytosis, exocytosis.
Water moves from low solute (high water potential) to high solute (low water potential). Cell in hypertonic solution shrivels (water leaves). Hypotonic = swells. Isotonic = no net change. Direction follows water, not solutes.
| Level | Definition |
|---|---|
| Population | same species, same area |
| Community | multiple populations interacting |
| Ecosystem | community + abiotic environment |
| Biome | large region, similar climate + life |
| Biosphere | all ecosystems |
Exponential: dN/dt = rN → N(t) = N₀ e^(rt)Logistic: dN/dt = rN(1 − N/K) K = carrying capacity| Type | Effect on A | Effect on B |
|---|---|---|
| Mutualism | + | + |
| Commensalism | + | 0 |
| Parasitism | + | − |
| Predation | + | − |
| Competition | − | − |
Energy flow: producers (autotrophs) → primary consumers → secondary → tertiary. ~10% energy transfer per trophic level (rest as heat). Why food chains are short.
K is the equilibrium population the environment can sustain — populations oscillate around K, not always below. K can change (drought, fires, human impact). Don't confuse with peak observed population.
| Phase | What happens | Duration |
|---|---|---|
| G1 | cell grows, normal function | ~10 hr |
| S | DNA replication | ~6-8 hr |
| G2 | further growth, prep for mitosis | ~3-4 hr |
| M | mitosis + cytokinesis | ~1 hr |
| G0 | quiescent (non-dividing) | indefinite |
DNA replication: semiconservative — each new strand pairs with original| Enzyme | Function |
|---|---|
| Helicase | unwinds DNA |
| Primase | lays RNA primers |
| DNA pol III | 5' → 3' synthesis |
| Ligase | seals Okazaki fragments |
| Topoisomerase | relieves supercoiling |
Leading vs lagging: leading strand synthesized continuously toward fork. Lagging synthesized in discontinuous Okazaki fragments (5' → 3' rule).
Mitosis: 1 division → 2 identical diploid cells (2n → 2n). For growth + repair. Meiosis: 2 divisions → 4 haploid cells (2n → n). For gametes. Meiosis I separates homologs; meiosis II separates sisters (like mitosis).
| Mechanism | Effect |
|---|---|
| Natural selection | differential survival/reproduction |
| Genetic drift | random allele frequency change (small pops) |
| Gene flow | migration between populations |
| Mutation | raw material — slow |
| Non-random mating | e.g. sexual selection |
p² + 2pq + q² = 1 where p + q = 1 (allele frequencies)5 conditions for HWE: large pop, no mutation, no migration, random mating, no selection. None met in real populations — HWE serves as a null hypothesis against which evolution is measured.
Speciation: reproductive isolation → divergence. Allopatric (geographic separation) is most common; sympatric (in same area, e.g. polyploidy in plants) is rarer.
Fitness = reproductive success (how many offspring survive to reproduce). Not 'physically fit' or 'best at survival.' A small, sneaky organism with many offspring can be fitter than a strong one with few. Selection acts on reproductive output, not lifespan or strength alone.
| System | Main organs | Function |
|---|---|---|
| Circulatory | heart, vessels, blood | transport O₂, nutrients, waste |
| Respiratory | lungs, trachea | gas exchange (O₂ in, CO₂ out) |
| Digestive | stomach, intestines, liver | break down food, absorb nutrients |
| Nervous | brain, spinal cord, nerves | signaling, control |
| Endocrine | glands (pituitary, thyroid) | hormones, slow signaling |
| Immune | WBC, lymph nodes | defense |
| Excretory | kidneys, bladder | waste filtration |
Immune system layers: innate (skin, inflammation, NK cells) responds in minutes. Adaptive (B + T cells) responds in days but specific. Memory cells mediate vaccine effectiveness.
Nervous vs endocrine: nerves use electrical signals, fast (ms). Endocrine uses hormones, slow (sec to days), but reaches all body cells.
Negative feedback reverses change → maintains homeostasis (most physiology). Positive feedback amplifies → reaches an end point (childbirth, blood clotting). Most homeostatic loops are negative; positive is the exception, used for processes that need to run to completion.
| Law | Statement |
|---|---|
| Segregation | each parent gives one allele per gene to each gamete (random) |
| Independent assortment | different genes inherit independently (if on different chromosomes) |
| Dominance | dominant allele masks recessive in heterozygote |
Genotype: AA, Aa, aa Phenotype: dominant (AA, Aa) vs recessive (aa)| Concept | Definition |
|---|---|
| Test cross | cross unknown × homozyg recessive to reveal genotype |
| Incomplete dominance | heterozygote is intermediate (red × white = pink) |
| Codominance | both alleles expressed (AB blood type) |
| Pleiotropy | one gene affects multiple traits |
| Epistasis | one gene masks another (coat color in mice) |
Sex-linked: X-linked recessive shows up in males more (only 1 X). Color blindness, hemophilia. Mother carrier × father normal → 50% sons affected, 0% daughters affected (but 50% carriers).
Genes on the same chromosome are linked → don't assort independently → ratio deviates from 9:3:3:1. Recombination frequency tells how far apart they are. Always check whether genes are linked before applying the standard ratio.
DNA →[transcription]→ RNA →[translation]→ PROTEIN| Step | What happens |
|---|---|
| 1. Initiation | RNA pol binds promoter (TATA box) |
| 2. Elongation | RNA pol synthesizes mRNA 5' → 3' (template read 3' → 5') |
| 3. Termination | RNA pol falls off at terminator |
| 4. Processing | 5' cap, 3' poly-A tail, splice introns out (eukaryotes only) |
| Mutation type | Effect |
|---|---|
| Silent | codon → same AA (3rd position often) |
| Missense | codon → different AA |
| Nonsense | codon → stop (truncated protein) |
| Frameshift | insertion/deletion shifts reading frame (catastrophic) |
Gene regulation: prokaryotes use operons (lac, trp). Eukaryotes use enhancers, transcription factors, alternative splicing, miRNA, chromatin remodeling.
RNA pol reads template strand 3' → 5' while synthesizing mRNA 5' → 3'. The other DNA strand (coding strand) has the same sequence as mRNA (with T → U). Don't confuse: synthesis direction is fixed by enzyme; reading direction is opposite.
| Keyword | Use § from | Approach |
|---|---|---|
| 'prokaryote vs eukaryote' | § ① | nucleus, organelles, ribosome size |
| 'mitochondria origin' | § ① | endosymbiotic theory: own DNA, 70S, double membrane |
| 'osmosis / hyper/hypotonic' | § ① | water moves to high solute; cell shrinks/swells |
| 'active vs passive transport' | § ① | active needs ATP, against gradient |
| 'cell cycle phases' | § ② | G1, S (DNA syn), G2, M (mitosis); checkpoints |
| 'mitosis vs meiosis' | § ② | 1 division → 2n+2n; 2 divisions → 4 haploid |
| 'leading vs lagging strand' | § ② | 5'→3' synthesis; lagging in Okazaki fragments |
| Punnett square / cross | § ③ | list parental gametes, fill grid, count phenotypes |
| '3:1 ratio' / 'monohybrid' | § ③ | Aa × Aa, 3:1 dominant:recessive |
| '9:3:3:1 ratio' / 'dihybrid' | § ③ | independent assortment, AaBb × AaBb |
| X-linked, sex-linked | § ③ | males show recessive at higher rate |
| 'incomplete dominance / codominance' | § ③ | blend vs both expressed |
| 'transcription / translation' | § ④ | DNA → mRNA → protein; codon table |
| 'mutation type' | § ④ | silent / missense / nonsense / frameshift |
| 'lac operon' | § ④ | prokaryote regulation: lactose ↑ → inducer binds repressor → transcription on |
| Hardy-Weinberg, p² + 2pq + q² | § ⑤ | find q from q²; p = 1−q; 2pq for heterozygotes |
| 'natural selection / fitness' | § ⑤ | differential reproduction; selection on allele frequency |
| 'genetic drift / bottleneck' | § ⑤ | random change in small populations |
| 'speciation, allopatric' | § ⑤ | geographic isolation → divergence → reproductive isolation |
| 'population growth' / 'logistic' | § ⑥ | r vs K, dN/dt = rN(1 − N/K) |
| 'energy pyramid' / '10% rule' | § ⑥ | each trophic level loses ~90% as heat |
| 'predator/prey, mutualism' | § ⑥ | +/+, +/0, +/−, −/− table |
| 'homeostasis / negative feedback' | § ⑦ | regulator detects change → reverses it (insulin, sweat) |
| 'innate vs adaptive immunity' | § ⑦ | innate fast non-specific; adaptive slow specific + memory |
'Mice with high cholesterol live longer.' Could be: (a) cholesterol helps, (b) reverse cause, (c) third variable (genetics, diet). To prove (a), RCT: randomly raise cholesterol, see if lifespan increases. Same logic as in psychology.
BIO 101 wants the names: Mendel (1865), Darwin (1859), Hardy + Weinberg (1908), Watson + Crick (1953), Meselson + Stahl (1958). Knowing who/when earns easy MC points.